Historical
NFPA 499-2004
NFPA 499: Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 2004 Edition
Applies to those locations where combustible dusts are produced, processed, or handled and where dust released into the atmosphere or accumulated on surfaces may be ignited by electrical systems or equipment.
National Fire Protection Association [nfpa]